fix: remove inconsistent model variable naming (#1701)

fix: remove inconsistent model variable naming in
evaluate_models_in_vertex_ai_studio_and_model_garden.ipynb


Fixes #1691  🦕

gemini/evaluation/evaluate_models_in_vertex_ai_studio_and_model_garden.ipynb

@@ -1602,7 +1602,7 @@
         "for i, prompt_template in enumerate(prompt_templates):\n",
         "    eval_result = summarization_eval_task.evaluate(\n",
         "        prompt_template=prompt_template,\n",
-        "        model=model,\n",
+        "        model=gemini_model,\n",
         "        # Customize eval service rate limit based on your project's Gemini-1.5-pro model quota to improve speed.\n",
         "        # See more details in https://cloud.google.com/vertex-ai/generative-ai/docs/models/run-evaluation#increase-quota\n",
         "        evaluation_service_qps=1,\n",